The present invention is directed to sensing and controlling the level of fluids, and more particularly to sensing and controlling the level of biofluid within drop ejection devices.
Various designs have been proposed for the ejection of biofluids which permit the high-speed printing of sequences and arrays of drops of biofluids to be used in various tests and experiments. In the present discussion, a biofluid, also called a reagent, may be any substance used in a chemical reaction to detect, measure, examine or produce other substances, or is the substance which is to be detected, measured, or examined.
Biofluid ejection devices find particular utility in the depositing of drops on to a substrate in the form of a biological assay. For example, in current biological testing for genetic defects and other biochemical aberrations, thousands of the individual biofluids are placed on a glass substrate at different well-defined locations. Thereafter, additional depositing fluids may be deposited on the same locations. This printed biological assay is then scanned with a laser in order to observe changes in an optical property, such as fluorescence.
It is critical in these situations that the drop ejection device not be a source of contamination or permit unintended cross-contamination between different biofluids.
As these biofluids have a high cost, it is desirable to use only small volumes in the testing operations and to ensure the ejected drops are, in addition to being non-contaminated, fully formed. This requirement raises an issue as to proper level control of the biofluid and priming of ejection devices in order to generate a most efficient and useful drop output.
In view of the foregoing, it has been considered desirable to provide mechanism which ensure the proper delivery of biofluids to an ejector device in a timely, useful manner.
A level control mechanism is provided for a biofluid drop ejection device which ejects biofluid drops in small volumes. The biofluid drop ejection device includes a drop ejection mechanism having a transducer which generates energy used to emit the biofluid drops. A reagent cartridge or biofluid holding area holds a biofluid, isolated from the drop ejection mechanism to avoid contamination between the biofluid drop ejection mechanism and the reagent cartridge. The reagent cartridge is connected to the drop ejection mechanism such that upon operation of the mechanism, the biofluid is emitted in controlled biofluid drops. A level sensor is positioned to sense a height of the biofluid within the cartridge. Upon sensing the height of the biofluid below a certain level, an adjustment is made to the height by providing at least one of additional biofluid to the cartridge, and raising the level of the entire reagent cartridge.